CT imaging findings of acute mesenteric ischemia and ischemic colitis. A brief pictorial essay.

Transcription

1 CT imaging findings of acute mesenteric ischemia and ischemic colitis. A brief pictorial essay. Poster No.: C-0750 Congress: ECR 2011 Type: Educational Exhibit Authors: Y. Arias Morales, J. P. Giraldo Marin, M. E. Salazar Salazar, L. Casal Da Vila, P. Prieto; Ourense/ES Keywords: Abdomen, Small bowel, Colon, CT, Diagnostic procedure, Acute, Ischemia / Infarction DOI: /ecr2011/C-0750 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 23

2 Learning objectives Review etiology and pathology of mesenteric ischemia and ischemic colitis. Describe its most common imaging findings on CT. Background Acute bowel ischemia includes a wide spectrum which classically is classified as mesenteric ischemia and ischemic colitis. The disease severity depends on the acuteness, duration, degree, state of the collateral circulation, extension of the involved area and promptness of therapeutic intervention. The ischemic damage starts in the mucosa, extends outward through the submucosa and proper muscular layer, and ends at serosa. Damage severity ranges from mucosal, mural to transmural necrosis. Acute mesenteric ischemia is a life compromising condition with a high reported mortality rate (50-90%), which requires an early diagnosis and treatment [1]. Its severity ranges from mild, with transient changes of intestinal mucosa, to highly dangerous and life threatening transmural intestinal necrosis [2]. Ischemic colitis usually appears as a mild and reversible condition, but 15-20% of patients may present a severe life threatening affectation. Table 1. Page 2 of 23

3 Fig. References: Y. Arias Morales; Radiologia, Complexo Hospitalario de Ourense, Ourense, SPAIN Exist several causes of insufficient intestinal blood flow (table 1) on page as thromboembolism (fig. 1) on page 4, neoplasm, intestinal obstruction, vasculitis, abdominal inflammatory conditions, chemotherapy, radiation, corrosive injury, nonocclusive causes (cardiac disease, hypotension, hypoperfusion) and others [3]. Page 3 of 23

4 Fig.: Mesenteric superior artery occlusive thromboembolism. References: Y. Arias Morales; Radiologia, Complexo Hospitalario de Ourense, Ourense, SPAIN CT is the first line diagnostic procedure in mesenteric ischemia, therefore colonoscopy still being most trusted diagnostic method for ischemic colitis. This exhibit provides a brief review about radiologic manifestations of mesenteric ischemia and ischemic colitis, emphasizing CT findings in 10 patients. Images for this section: Page 4 of 23

5 Fig. 1: Mesenteric superior artery occlusive thromboembolism. Page 5 of 23

6 Imaging findings OR Procedure details CT findings in acute mesenteric ischemia and ischemic colitis include various morphologic changes as bowel wall thickening, bowel dilatation, mesenteric fat stranding, ascitis, bowel wall attenuation or abnormal enhancement, pneumatosis and portal venous gas (tab. 2) on page 13. Table 2. Fig. References: Y. Arias Morales; Radiologia, Complexo Hospitalario de Ourense, Ourense, SPAIN Those changes may appear in small and large bowel affectation, may be localized or diffuse, superficial or transmural and may simulate various intestinal diseases, becoming heterogeneous and nonspecific. Often, clinical and laboratory findings are Page 6 of 23

7 nonspecific too, making radiologic diagnosis more difficult in absence of typical imaging manifestations [2]. The most common CT finding in acute bowel ischemia is bowel wall thickening (fig. 2) on page 14. It is due to edema, hemorrhage or superinfection of the ischemic bowel wall and may be associated to hypoattenuation (edema) or hyperattenuation (hemorrhage, hyperemia, hyperperfusion). Fig.: Mesenteric ischemia CT imaging findings: bowel wall thickening, abnormal wall enhancement, mesenteric fat stranding and ascitis. References: Y. Arias Morales; Radiologia, Complexo Hospitalario de Ourense, Ourense, SPAIN Wall thickening is a typical finding in cases of reversible mesenteric ischemia (associated with good prognosis), ischemic colitis (fig. 3) on page 15, colonic infarction, and Page 7 of 23

8 acute bowel ischemia related to mesenteric venous occlusion. The degree of bowel wall thickening does not correlate with the severity of damage. It is not common in arterial occlusion small bowel infarction, where the necrotic bowel shows fluid filled loops and a thin, unenhanced wall. In nontransmural ischemic colitis, wall thickening may be very pronounced due to submucosal hemorrhage, inflammation and superinfection making it indistinguishable from transmural colonic infarction, if no other sugestive findings are associated. Unfortunately wall thickening is also the less specific CT finding, because it may be found in variable diseases and no ischemic conditions [2]. Fig.: Ischemic colitis CT imaging and colonoscopy findings. References: Y. Arias Morales; Radiologia, Complexo Hospitalario de Ourense, Ourense, SPAIN Page 8 of 23

9 Bowel dilatation, associated to fluid filled loops, is a common finding in intestinal infarction, but it is rare in superficial ischemic colitis and reversible bowel ischemia. It may result from interruption of intestinal peristalsis caused by ischemic injury and from irreversible ischemic damage (fig. 4) on page 16. Mesenteric fat stranding, ascitis or mesenteric fluid, are nonspecific findings. Their presence is related to the cause, pathogenesis, and severity of the ischemia. Those findings may be seen associated to small bowel ischemia caused by mesenteric venous occlusion, wich causes transudation into the mesentery or the peritoneal cavity. In large bowel ischemia, mesenteric fat stranding and ascitis are related to superinfection of damaged colonic wall, but do not allow differentiation between transmural and partial mural colonic ischemia (ischemic colitis), in abscense of additional sugestive signs. Fig.: Irreversible ischemic damage in mesenteric ischemia and ischemic colitis. References: Y. Arias Morales; Radiologia, Complexo Hospitalario de Ourense, Ourense, SPAIN Page 9 of 23

10 Hyperemia and hyperperfusion may cause hyperattenuation. A unenhanced CT before a contrast enhanced CT, may help differentiate between acute intramural hemorrhage/ hyperemia and hyperperfusion. Hyperemia without hyperperfusion may be seen in mesenteric venous occlusion and subsequent outflow obstruction. Hyperemia and hyperperfusion may cause a "target sign" (fig. 5) on page 17 when affected mucosa and submucosa are surrounded by mural edema. This is a typical finding in mesenteric venous occlusion. Fig.: "Target sign" in mesenteric venous occlusion. References: Y. Arias Morales; Radiologia, Complexo Hospitalario de Ourense, Ourense, SPAIN Absence of wall enhancement, in intravenous contrast enhanced studies, is highly specific for acute mesenteric ischemia. This finding may appear associated with a "paper thin wall" (fig. 6) on page 18 and fluid filled dilated loops. The pronounced wall thinning Page 10 of 23

11 ("paper thin wall") and loops dilatation result from destruction of intramural nerves and intestinal musculature, with the subsequent total loss of tone of the bowel wall. Fig.: "Paper thin wall" in small bowel infarction. References: Y. Arias Morales; Radiologia, Complexo Hospitalario de Ourense, Ourense, SPAIN Pneumatosis and portal venous gas are uncommon but highly specific findings. The pneumatosis appearance may vary from small bubbles inside an ischemic wall (fig. 7) on page 19, to a two layers dissected bowel wall (fig. 8) on page 20. Portal venous gas may have intrahepatic extension, with ominous prognosis associated. Page 11 of 23

12 Fig.: Bubble-like pneumatosis in ileum and transmural colonic infarction. References: Y. Arias Morales; Radiologia, Complexo Hospitalario de Ourense, Ourense, SPAIN Page 12 of 23

13 Fig.: Band-like pneumatosis in occlusive colonic overdistention. References: Y. Arias Morales; Radiologia, Complexo Hospitalario de Ourense, Ourense, SPAIN Images for this section: Page 13 of 23

14 Fig. 1 Page 14 of 23

15 Fig. 2: Mesenteric ischemia CT imaging findings: bowel wall thickening, abnormal wall enhancement, mesenteric fat stranding and ascitis. Page 15 of 23

16 Fig. 3: Ischemic colitis CT imaging and colonoscopy findings. Page 16 of 23

17 Fig. 4: Irreversible ischemic damage in mesenteric ischemia and ischemic colitis. Page 17 of 23

18 Fig. 5: "Target sign" in mesenteric venous occlusion. Page 18 of 23

19 Fig. 6: "Paper thin wall" in small bowel infarction. Page 19 of 23

20 Fig. 7: Bubble-like pneumatosis in ileum and transmural colonic infarction. Page 20 of 23

21 Fig. 8: Band-like pneumatosis in occlusive colonic overdistention. Page 21 of 23

22 Conclusion CT has emerged as the first line imaging method for assessing acute bowel ischemia, its complications and possible causes. Therefore, mesenteric ischemia and ischemic colitis may simulate many other clinical conditions, making CT essential for confirming or excluding these other diseases. Knowing most common and specific imaging findings helps toward an early and accurate diagnosis, which often determines optimal treatment and may reduce mortality. Personal Information Dr. Yeison Arias Morales, Dr. Juan Pablo Giraldo Marin, Dra. Mariana Salazar Salazar, Dra. Laura Casal Da Vila, Dr. Pedro Prieto Casal. Radiology department. Complexo Hospitalario de Ourense. Ourense, Galicia, Spain. References 1. Furukawa A et al. CT diagnosis of acute mesenteric ischemia from various causes. AJR 2009; 192: Wiesner W, Khurana B, Ji H, Ros P. CT of acute bowel ischemia. Radiology 2003; 226: Rha SE et al. CT and MR imaging findings of bowel ischemia from various primary causes. RadioGraphics 2000; 20: Chou CK. CT Manifestations of bowel ischemia. AJR 2002; 178: Horton KM, Fishman EK. Multi-detector row CT of mesenteric ischemia: can it be done? RadioGraphics 2001; 21: Page 22 of 23

23 6. Bradbury MS et al. Mesenteric venous thrombosis: diagnosis and noninvasive imaging. RadioGraphics 2002; 22: Sheedy SP, Earnest F, Fletcher J, fiddler J, Hoskin T. CT of small-bowel ischemia associated with obstruction in emergency department patients: diagnostic performance evaluation. Radiology 2006; 241: Wittenberg J, Harisinghani M, Jhaveri K, Varghese J, Mueller P. Algorithmic approach to CT diagnosis of the abnormal bowel wall. RadioGraphics 2002; 22: Zalcman M, Sy M, Donckier V, Closset J, Gansbeke DV. Helical CT signs in the diagnosis of intestinal ischemia in small bowel obstruction. AJR 2000; 175: Thoeni RF, Cello JP. CT imaging of colitis. Radiology 2006; 240: Page 23 of 23